The Lung Health Study (LHS), conducted from 1986-1994, demonstrated that a smoking intervention program in middle-aged long-term cigarette smokers can result in a highly significant beneficial effect on the rate of FEV1 decline over five years. However, FEV1 is only a surrogate marker for clinical outcomes of respiratory morbidity and mortality. The present study proposes long-term post-trial follow-up of former LHS participants to assess the incidence of morbidity and mortality from respiratory and cardiovascular diseases and other causes, as documented by hospital, clinic, and death records. A lung function test 11 to 12 years after entry into the LHS is also proposed to determine long-term effects of smoking cessation on lung function. The main objectives of the study are as follows: 1) to determine, using an intent-to-treat analysis, whether the LHS smoking intervention significantly reduces the incidence of clinically important respiratory cardiovascular disease over a 12- to 15-year period following study enrollment; 2) to determine whether the beneficial effect of the smoking intervention program on measures of lung function persists through 11 to 12 years of follow-up; 3) to estimate the magnitude of the effects of FEV1 and FVC on the risks of cardiovascular and respiratory morbidity and mortality, after controlling for smoking history; 4) to study the role of other factors [gender, airways, reactivity, weight gain, and co- morbidities] in determining the rate of decline in pulmonary function and the risks of cardiovascular and respiratory morbidity and mortality. All ten of the original LHS clinical centers plan to participate. To minimize bias, all surviving participants of the LHS will be invited to participate, giving a potential sample size of 5600.